PROJECT SUMMARY/ABSTRACT Microsurgical models of murine organ transplantation have played a critical role in advancing our understanding of immunological pathways that regulate graft rejection and tolerance. Such models are important tools to develop therapies for transplant patients. Importantly, substantial differences exist between immune responses to various grafts. Since the initial description of the orthotopic mouse lung transplant model by our laboratory we and others have relied on this technique to investigate lung-specific alloimmune responses. The overall goal is to establish a dedicated microsurgery core to facilitate the execution of experiments described in this program project. In aim 1 we will establish a system to provide unfettered access to microsurgical transplants for all three projects in this proposal. We plan to accomplish this by coordinating access and timing of surgical procedures. In aim 2 we will focus on standardizing the quality of microsurgical procedures for all three projects. We will accomplish this through systematic standardization of microsurgical procedure between all surgeons. In aim 3 we plan to standardize techniques of intravital two- photon microscopy, a novel technique utilized by all three projects. In aim 4 we plan to standardize assessment of graft function and tissue harvest.